A question for gun experts

My family and I were discussing an old Columbo episode in which the victim was killed by a particular caliber of bullet. The suspect that Columbo tailed for the entire episode (Robert Culp), though he owned handguns, owned none of the caliber that was used in the murder.

At the end, Columbo proves the murderer guilty by discovering an item hidden in a lamp. "A calibration converter," he says. "That was a sweet touch. I never would have thought of that." And we see that the calibration converter is a cylindrical device which slides into the barrel of a handgun.

Now, one of us in the discussion is studying criminal justice, and neither he nor the rest of us had ever heard of a calibration converter. Nor could we figure out how, if this device slips into the barrel of a gun, it isn't violently ejected when one fires the weapon.

I Googled this term, and most of what I came up with was either electronics, or other references to that Columbo episode. I even checked a handgun site and found nothing about it. Only one web page made a passing mention of it, and I think they were talking guardedly about using weapons for illegal purposes.

So does anybody know about calibration converters? I'm just curious, because if it weren't for the reference above, I'd be tempted to pass it off as a Hollywood scriptwriter's invention. And if they're real, how do you keep them from ejecting when the gun is fired? Does this device have any legitimate purposes, or is it mainly designed to deceive law enforcement? If the latter, how come you don't hear more about criminals using them?

Yes it a real item, Heckler and Koch supply a converter to the MP5 and others that take the caliber down to .22 for room clearence, stops the 9mm rounds from going through walls and killing civillians.

It's as you describe, a sleeve that fits into the barrel and a different feed mechanism.

Actually, such a device was mentioned in Tom Clancy's Without Remorse . The protagonist used one to convert a .45 into a .22. Yes, I know it's a book and a work of fiction at that, but Clancy is usually very good in being as realistic as possible when it comes to technological matters and whatnot.

Actually, such a device was mentioned in Tom Clancy's Without Remorse . The protagonist used one to convert a .45 into a .22. Yes, I know it's a book and a work of fiction at that, but Clancy is usually very good in being as realistic as possible when it comes to technological matters and whatnot.

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I read that book and really liked it.

One reason to use one is that since .22 rounds are really cheap you can convert your .45 down to one to practice and save money.

Yes it a real item, Heckler and Koch supply a converter to the MP5 and others that take the caliber down to .22 for room clearence, stops the 9mm rounds from going through walls and killing civillians.

It's as you describe, a sleeve that fits into the barrel and a different feed mechanism.

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For a lecturer in music(?) you seem to know a lot about this . Much call for it with your students?

Not to hijack this thread, but what do the differences in calibers of bullets do?

I was under the impression that the bigger the caliber, the less likely it's to pierce armor. For example, in Rainbow Six (the game), the 9mm MP5's don't easily kill your opponents quickly when you hit them at the torso and, they have body armor. But, take something like an M16 with its 5.56, it pierces right through and is almost always one-shot-one-kill.

Also, I've heard on the news, or read in books or articles, the 7.62 or 5.56 are usually seen as deadly. So, my info is not just based on video games!

Then taking another look at the actual bullets, it seems like the 9mm is blunt and the 5.56 or 7.62 are pointier. So, it's more about the shape, then?

Then you've got your .22, .45, .50, etc. calibers... (American measurements, I assume? Are we measuring those in inches or what?)

For a lecturer in music(?) you seem to know a lot about this . Much call for it with your students?

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Nah, that's what the aikido's for....

My ex-brother-in-law was a Royal Marine, and I know a couple of UK special forces types from the martial arts circuit, I've done a couple of SAS training days and courses, mainly for the unarmed stuff, but also for weapons and tactics.

I know UK schools are getting more violent, but I don't think firearms are the answer just yet.

Not to hijack this thread, but what do the differences in calibers of bullets do?

I was under the impression that the bigger the caliber, the less likely it's to pierce armor. For example, in Rainbow Six (the game), the 9mm MP5's don't easily kill your opponents quickly when you hit them at the torso and, they have body armor. But, take something like an M16 with its 5.56, it pierces right through and is almost always one-shot-one-kill.

Also, I've heard on the news, or read in books or articles, the 7.62 or 5.56 are usually seen as deadly. So, my info is not just based on video games!

Then taking another look at the actual bullets, it seems like the 9mm is blunt and the 5.56 or 7.62 are pointier. So, it's more about the shape, then?

Then you've got your .22, .45, .50, etc. calibers... (American measurements, I assume? Are we measuring those in inches or what?)

Explain, gun experts!

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5.56, 7.62 and 9 are all mm. .22, .45, .50 are inches. The power is to do with velocity. Weight of ammunition has an effect as well. 5.56 and 7.62 are usually rifle ammunition (usually military or miltary style). .45 and .50 are handgun ammo. The exception being .50 cals you see mounted on Humvees and helicopters. .22 is a low calibre, lightweight rifle weapon with limited power and range used for hunting (animals not men).

5.56, 7.62 and 9 are all mm. .22, .45, .50 are inches. The power is to do with velocity. Weight of ammunition has an effect as well. 5.56 and 7.62 are usually rifle ammunition (usually military or miltary style). .45 and .50 are handgun ammo. The exception being .50 cals you see mounted on Humvees and helicopters. .22 is a low calibre, lightweight rifle weapon with limited power and range used for hunting (animals not men).

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The smaller calibers means they're lighter making it easier to launch at higher velocities and making them deadlier, correct?

And of course there's the exceptions such as the .50 which are deadly as vehicle-mounted weapons.

To further explain, you can get handguns down to to smaller callibers, but it's fairly pointless as anything less than a 22 isn't going to do much of anything. 22 would be a good home-defense, would-tear-open-a-kneecap weapon. It goes up from there, I would say .45 is a really bad choice for most handgun owners, because even if it's compensated, the recoil would screw your aim... Anyone considering a handgun should go to a shooting range and try a couple out to see what you're comfortable with. Getting too large a caliber will do no good.

The smaller calibers means they're lighter making it easier to launch at higher velocities and making them deadlier, correct?

Thanks for the explanation. It makes sense.

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No that's the wrong way round. They do have higher velocities but a lower mass. Force = mass x velocity. Rifles can fire heavier bullets because the barrels can withstand more pressure. See here for a more technical explanation. Don't believe everything you see in videogames

No that's the wrong way round. They do have higher velocities but a lower mass. Force = mass x velocity. Rifles can fire heavier bullets because the barrels can withstand more pressure. See here for a more technical explanation. Don't believe everything you see in videogames

The smaller calibers means they're lighter making it easier to launch at higher velocities and making them deadlier, correct?

And of course there's the exceptions such as the .50 which are deadly as vehicle-mounted weapons.

Thanks for the explanation. It makes sense.

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The makeup of a bullet is more critical than its caliber. A hollowpoint is going to behave differently than an armour-piercing round. In some cases, a small armour-piercing round is ideal and in others they're nearly worthless. Generally speaking, a soft target needs a soft bullet.

The bullet is decelerating virtually the instant it leaves the barrel.

I think that force = mass X velocity is more accurate because how much force depends on exactly how fast the bullet is traveling at the point of impact mutliplied by its mass, which remains virtually unchanged once it leaves the barrel i.e. there will be a lot more force involved a short distance from the barrel than 1 mile from it.

As for the size and the weight of the bullet. It requires a lot less energy to launch a low mass at a high velocity than a much heavier mass to the same velocity. Coupled with the fact that a low mass bullet will dissipate its energy a lot faster than a heavier one. Another added advantage is that because less energy is required, the gun will kick less and hence be a lot easier to control.

Just to put things in perspective, an average 9mm bullet weighing 115 grains usually has a muzzle velocity of around 400meters/second. An average 230 grain 45 caliber bullet has a muzzle velocity of around 280meters/second. A 50 grain 5.56mm bullet has a sizzling muzzle velocity of around 1000meters/second. And NATO's old round, the 125 grain 7.62mm has a muzzle velocity of around 800meters/second.

I was under the impression that the bigger the caliber, the less likely it's to pierce armor. For example, in Rainbow Six (the game), the 9mm MP5's don't easily kill your opponents quickly when you hit them at the torso and, they have body armor. But, take something like an M16 with its 5.56, it pierces right through and is almost always one-shot-one-kill.

Also, I've heard on the news, or read in books or articles, the 7.62 or 5.56 are usually seen as deadly. So, my info is not just based on video games!

Then taking another look at the actual bullets, it seems like the 9mm is blunt and the 5.56 or 7.62 are pointier. So, it's more about the shape, then?

Then you've got your .22, .45, .50, etc. calibers... (American measurements, I assume? Are we measuring those in inches or what?)

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The barrel of a gun has a lot to do with how the gun hits and kills. If the barrel has grooves in it, the bullet will spin (like a football) and be more accurate and deadly, for when it hits a target it rips through into their insides. An M-16's round actually tumbles through the air so that when it hits a target, it destroys the targets insides.

9mm, 5.56mm, .22 caliber, all refer to diameter. Tanks can have a 105mm gun. A .45 caliber pistol means the bullet is .45 inches in diameter.

That's why a .45 and a .50 are so devastating-- they are simply larger bullets. In WWII, B-17s had a number of .50 cal guns on them. They would fire back at fighters incoming. If they contacted an enemy fighter in the right spot they could sometimes blow the wing clear off.

The bullet is decelerating virtually the instant it leaves the barrel.

I think that force = mass X velocity is more accurate because how much force depends on exactly how fast the bullet is traveling at the point of impact mutliplied by its mass, which remains virtually unchanged once it leaves the barrel i.e. there will be a lot more force involved a short distance from the barrel than 1 mile from it.

As for the size and the weight of the bullet. It requires a lot less energy to launch a low mass at a high velocity than a much heavier mass to the same velocity. Coupled with the fact that a low mass bullet will dissipate its energy a lot faster than a heavier one. Another added advantage is that because less energy is required, the gun will kick less and hence be a lot easier to control.

Just to put things in perspective, an average 9mm bullet weighing 115 grains usually has a muzzle velocity of around 400meters/second. An average 230 grain 45 caliber bullet has a muzzle velocity of around 280meters/second. A 50 grain 5.56mm bullet has a sizzling muzzle velocity of around 1000meters/second. And NATO's old round, the 125 grain 7.62mm has a muzzle velocity of around 800meters/second.

Maybe somebody can post the conversion of grains to grams.

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14.3 grains = 1 gram. Long barreled weapons have less kick than short barreled ones. Muzzle velocity has very little to do with effect.
The barrel of a gun has a lot to do with how the gun hits and kills.
"If the barrel has grooves in it, the bullet will spin (like a football) and be more accurate and deadly, for when it hits a target it rips through into their insides. An M-16's round actually tumbles through the air so that when it hits a target, it destroys the targets insides." All barrels have grooves - this is how the bullet flies straight (ish). Low range weapons, like the M-16, are deliberately designed so that the bullet "tumbles". The bullet tumbling carries a lot of kinetic energy and will cause a lot of damage once it hits a target. It is not, however, particularly accurate over a long distance. For that you need a well grooved barrel and heavy ammunition. The bullet does not tumble over distance so you are relying on a well placed shot ie. along the "T" from the forehead across the brain, down through the major internal organs, to achieve a "kill" shot. The bullet has less effect than the trauma to the major organs.

I'm not sure how many of you are from over seas, but there is a desire among the anti-gun lobby in America to "fingerprint" all guns at the time of manufacture. It's based upon the mistaken belief that police could solve more gun-related crimes because there would be a database of ballistic "fingerprints" that would help trace the gun. It is my understanding that it only takes a metal rod (not the kind for cleaning guns) to scrape the inside of a barrel, and the finger print is ruined. I don't if this comment is on topic, but your Colombo story made me think of it. Thinking people should find this obvious, but then again . . .

The bullet is decelerating virtually the instant it leaves the barrel.

I think that force = mass X velocity is more accurate because how much force depends on exactly how fast the bullet is traveling at the point of impact mutliplied by its mass, which remains virtually unchanged once it leaves the barrel i.e. there will be a lot more force involved a short distance from the barrel than 1 mile from it.

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Although it sounds like you know alot about bullets and guns, but, F=ma. Deceleration is acceleration, but negated. so, the force of a bullet is exactly when it leaves the barrel of the gun. Basically, take the initial speed, V0 = 0MPH and the V1 = 400MPH? (I don't know much about guns, just physics). From that, given delta t of the travel you can calculate the acceleration of the bullet. Then multiply this by the mass and you get the instantaneous force of the bullet. From there, you say the bullet is decelerating (due to resistance in some form, air, the wall, my leg, etc). So, do the same calculation for a different delta t, but with a negative acceleration. Then, you get a negative force. Add this negative force to the initial force from where the bullet left the barrel of the gun and you get the new instantaneous force. When the bullet stops, you should have 0 N of force if you have done all of your calculations correctly.

Hmm, it's been many decades since my last science and math classes, but I clearly remember the term velocity being used. The main reason being is that in certain situations terminal velocity is reached, and then the object is neither accelerating or decelerating - eg someone jumping out a plane - and will continue to do so until it collides with something.

I may be wrong about the exact term, so I'll have to check with my NASA aerospace friend to see what the preferred term is today.

Although it sounds like you know alot about bullets and guns, but, F=ma. Deceleration is acceleration, but negated. so, the force of a bullet is exactly when it leaves the barrel of the gun. Basically, take the initial speed, V0 = 0MPH and the V1 = 400MPH? (I don't know much about guns, just physics). From that, given delta t of the travel you can calculate the acceleration of the bullet. Then multiply this by the mass and you get the instantaneous force of the bullet. From there, you say the bullet is decelerating (due to resistance in some form, air, the wall, my leg, etc). So, do the same calculation for a different delta t, but with a negative acceleration. Then, you get a negative force. Add this negative force to the initial force from where the bullet left the barrel of the gun and you get the new instantaneous force. When the bullet stops, you should have 0 N of force if you have done all of your calculations correctly.

BEN

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you're correct, but i imagine everyone is wondering what the hell delta t is because you did not elaborate on it. you also didn't explain what instantaneous force is. i.e. i am sure everyone is confused by you explaination unless they took physics and calculus. but yeah, you are correct.

No problem. I'm learning more than I asked about. Although the question remains: how is the calibration converter held in place when the gun is fired? Does it screw in somehow?

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Some automatic handguns have complete interchangeable barrel/slide assemblies to facilitate a change in caliber, and some revolvers just require half moon clips e.g. a 38 special will require the half moon clips in order to take 9mm bullets. Because the diameter of both bullets is identical, no other change is required.

Also, if I recall correctly, Ruger made same revolvers where both the chamber and the barrel (which was screwed in) were swapped out in order to achieve the same thing.

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